Effect of bioagents on cucumber seed mycoflora, seed germination, and seedling vigour

The effect of different bioagents such as Trichoderma harzianum, T. viride, T. virens, Pseudomonas fluorescens, and Bacillus subtilis was studied on seed mycoflora, seed germination, root/shoot length, and seedling vigour of cucumber var. Solan Srijan under in vitro conditions. Alternaria sp., Aspergillus sp., and Fusarium spp. were observed on cucumber as seed mycoflora, with T. harzianum showing the greatest inhibition for Alternaria sp. and Fusarium spp., and T. viride showing the greatest inhibition for Aspergillus sp. Cucumber var. Solan Srijan seeds were treated with various bio agents, with T. harzianum being the most effective in increasing seed germination (88.75%), root length (13.58 cm), shoot length (14.58 cm), and seedling vigour (2501.31).

Effect of bio agents on seed germination and seedling vigour of cucumber. The results showed that all three Trichoderma spp. tested were effective in increasing the percentage of germination (Table 2). However, among the three species, T. harzianum (88.75%) significantly improved the germination percentage in cucumber seeds. In comparison to the control (62.50%), T. viride (82.50%) and T. virens (85.00%) efficiently improved seed germination. Seeds treated with Pseudomonas fluorescens (72.50%) and Bacillus subtilis (68.75%) germinated at a higher rate than control seeds. Overall cucumber seed germination percentage was highly increased by T. harzianum and least increased by Bacillus subtilis as compared to the control seeds. Bio agents produced considerably longer shoot and root lengths than the control (untreated) ( Table 2). In comparison to other bio agents, Trichoderma harzianum has the greatest potential to induce seedling root (13.58 cm) and shoot (14.58 cm) elongation. Trichoderma virens and Trichoderma viride were next with roots (13.00 cm, 12.06 cm) and shoots (13.86 cm, 13.26 cm) of different lengths, respectively. Bacillus subtilis had the shortest seedling length with a root and shoot length of 10.43 cm and 11.77 cm, respectively. Among the bio agents, the maximum seedling vigour index was observed in seed treatment with Trichoderma harzianum (2501.31) followed by seed treatment with Trichoderma virens (2286. 19) and the minimum vigour index was observed in seed treatment with Bacillus subtilis (1523.25) over untreated seeds having vigour index of 1100.75 (Table 2).

Discussion
The current findings are in agreement with those of Bharath et al. 4 ; Kakde and Chavan 9 ; Mogle and Maske 5 ; Singh et al. 10 ; Gawade et al. 6 , and Kumari 11 who reported T. harzianum's antagonistic activity against seed mycoflora. According to Kumari 11 , Trichoderma species have antagonistic activity against storage pathogens and contaminants such as Aspergillus spp., Penicillium spp. and Alternaria spp. Singh et al. 10 reported that Trichoderma harzianum, Pseudomonas fluorescens, Bacillus subtilis, T. virens and T. viride showed promising results against seed-borne fungi. Several cell wall degrading enzymes, such as chitinase and glucanase, play an important role in Trichoderma's antagonistic action against a wide range of fungal pathogens.
In the earlier studies, it was found that T. harzianum and T. viride have improved seed germination, root length and shoot length 12 . In the current study seeds treated with different bioagents had more seedling vigour and seed germination as compared to untreated seeds which means these treatments improve the seedling quality for growers. Seeds pretreated with Trichoderma viride, Trichoderma harzianum demonstrated enhanced seed germination rates and seedling vigour when compared to control seeds 13,14 . Kumari 11 found that Trichoderma Seed treatment. Seeds with no cracks or othesr visible deformations were selected and surface sterilised for 3-5 min in a 0.1% sodium hypochlorite solution. Subsequently, the seeds were rinsed three times with sterile distilled water, air dried, and soaked for 4 h in Trichoderma spp. (10 6 cfu/ml) and bacterial bioagents(10 8 cfu/ml) broth. The details of bio agents used for seed treatment are given in Table 3.
Seed mycoflora. The infestation of seed with mycoflora was observed using the standard Petri plate method, as recommended by ISTA 19 . Cucumber seeds were first treated with bioagents (Table 3) and then kept in Petri dishes (25 seeds per plate, 4 replications per treatment). These seeded plates were incubated at 25 °C for 7 days. Untreated seeds were used as control. The number of infected seeds was counted and the per cent inhibition of mycoflora was calculated using the following formula: Effect of bioagents on seed germination and seedling vigour of cucumber. Seeds of cucumber variety Solan Srijan were treated with different bioagents (Table 3) as mentioned earlier.
Effect on seed germination (%). According to ISTA, one hundred seeds per replication for each treatment were used to conduct the germination test 20 . This was done in the seed germinator at 25 °C using the paper roll and blotter paper method. After 4 and 8 days, the first and final counts were taken. The following formula was used to calculate the percentage of germination: Effect on mean shoot length (cm)/mean root length (cm). Ten normal seeds were chosen randomly during the final count on the 8th day. Their root and shoot lengths were measured in centimetres (cm) using a common ruler for all the seedlings.
Effect on seedling vigour. Seedling vigour was calculated as per the formula given by Abdul-Baki and Anderson 21 .

Statistical analysis.
All the experiments were carried out in a completely randomized design (CRD) with four replications. The collected data were subjected to one-way ANOVA. The significance of treatment means was practiced at a 5% level of probability 22 . Statistical analysis was done on OPSTAT software for the experiment (http:// 14. 139. 232. 166/ opstat/ ).

Inhibition of mycoflora (%) =
Total number of seeds − Number of infected seeds Total number of seeds × 100 Germination(%) = Number of seeds germinated Total number of seeds used × 100 Seedling vigour = Germination (%) × mean shoot length (cm) + mean root length (cm)